In C, the longest palindromic subsequence multithread exists

[Onam]

I'm learning how to multithread in C and figured the longest palindromic subsequence issue would be a good place to start.

To get the solution, we run two threads and compare their results. One thread is concerned with "odd" subsequences, whereas the other is concerned with "even" ones.

struct str* s0 = malloc(sizeof(struct str));
  struct str* s1 = malloc(sizeof(struct str));
  s0->seq = (char*)seq0;
  s1->seq = (char*)seq0;
  s0->len = len;
  s1->len = len;

  pthread_t t0;
  pthread_t t1;
  int* res0;
  int* res1;
  if (pthread_create(&t0, NULL, &odd, s0)!=0){
    return 0;
  }
  if (pthread_create(&t1, NULL, &even, s1)!=0){
    return 00;
  }
  if(pthread_join(t0, (void**)&res0)!=0){
    return 1;
  }
  if(pthread_join(t1, (void**)&res1)!=0){
    return 11;
  }

  if(*res0 > *res1){
    printf("%d\n", *res0);
  }else{
    printf("%d\n", *res1);
  }

  free(s0);
  free(s1);
  return 0;
}

Although the code appears to function, I'm curious about where in the application I should look for multi-threading issues. As I'm learning from this source, it's all new to me, thus I only need to know which portions may be prone to the troubles that multi-threading introduces.